1. Field of Invention
The present invention relates to an upper link for a utility vehicle, in particular for an agricultural tractor, wherein the upper link has a hydraulic cylinder for adjusting the upper link. Furthermore the present invention relates to a back-end and a front-end three-point hitch of a utility vehicle as well as to a utility vehicle with such a back-end and/or front-end mounted upper link.
2. Description of Related Art
Utility vehicles, in particular agricultural utility vehicles, such as for example an agricultural tractor, on the back-end and/or front-end often have a three-point hitch for attaching equipment. Such equipment may be an agricultural implement, such as for example a plough.
FIGS. 1 and 2 show a back-end three-point hitch with a conventional upper link. FIG. 1 is a perspective view of the conventional three-point hitch from the right in the driving direction and FIG. 2 shows a perspective view of the conventional three-point hitch from the left in the driving direction.
As is evident from FIGS. 1 and 2, the three-point hitch 2 is mounted on the back-end of the transmission. The three-point hitch 2 is formed by two lower links 6 and an upper link 8. The lower links 6 and the upper link 8 with their respective proximal end 6a or 8a are connected to the transmission case 4 (or possibly to chassis components). The distal ends 6b or 8b in each case have coupling elements 6c or 8c, which serve for coupling to a tool-carrying frame 10. The tool-carrying frame 10 for example forms part of a rear-mounted implement for back-end attachment to the utility vehicle, such as for example an agricultural plough. Here the sections of the lower links 6 and the upper link 8 which are arranged on the transmission case 4 are called “proximal”, while the sections remote from the transmission case 4 are called “distal”.
The lower links 6 are designed so as to actively pivot up and down. For this purpose the lower links 6 are connected to lift rods 11, which extend upwards from the lower links and with their upper end in turn are connected to elbow levers 12. As is generally known in this specialist area of engineering the elbow levers 12 can be pivoted by lift cylinders 14, as a result of which the lower links are raised or lowered. In the horizontal direction the lower links are designed so as to pivot back and forth to a limited extent or are rigid. The pendulum movement can be blocked by means of a control device. This blocking of the pendulum movement is activated primarily if the attachment has no contact with the ground. The upper link 8 can be likewise pivoted upwards and downwards about a linkage point 8a on the transmission case 4. Furthermore the length of the upper link 8 can be adjusted by a hydraulic cylinder 16.
Alternatively it is customary with conventional upper links that the lengthwise adjustment of the upper link is effected mechanically by means of a corresponding screw connection. By contrast the hydraulic adjustment of the upper link has the advantage that the upper link can also be adjusted under load. In mechanical adjustment (by screw adjustment) the upper link must be disengaged. Another disadvantage of mechanical adjustment is the susceptibility, in particular of the partially exposed adjustment thread, to contamination due to whirled up dust and thrown up earth. Furthermore provision of a hydraulic cylinder 16 has the advantage that the lengthwise adjustment of the upper link 8 can be controlled from the vehicle seat.
The tool-carrying frame 10 has two upwardly extending supports 17, which in each case are provided with drilled holes 18 in the form of borings. The drilled holes 18 here are arranged at different heights. In each case two drilled holes 18 are aligned with each other. Two elongated holes 20, which are aligned with each other and whose longitudinal direction runs transversely to the extension direction of the supports 17, are provided above the drilled holes 18 in the supports 17.
As is evident from FIGS. 1 and 2 the tool-carrying frame 10 is conventionally mounted on the three-point hitch 2 so that a lower part of the tool-carrying frame 10 is connected to the two coupling elements 6c of the lower links 6, while an upper part of the tool-carrying frame 10, in particular the two upper supports 17, is connected to the upper link 8. The lower part of the tool-carrying frame 10 in the present example is in the form of a transverse bar 24, while the coupling elements 6c of the lower links 6 are designed as hooks. In addition locking elements 6d, which engage above the bar 24 and thus prevent the transverse bar 24 from uncoupling, are provided on the hooks.
In order to connect the upper link 8 to the tool-carrying frame 10 a pin 22 is guided through a desired pair of drilled holes 18 or through the pair of elongated holes 20 and the coupling element 8c of the upper link 8 is hung on the pin. Similar to the lower links 6 the upper link 8 also has a hook, which is hung on the pin 22 from above, and (not illustrated) an engaging element, which prevents the hook uncoupling from the pin 22.
In principle, depending on the coupling variant of the upper link 8, two modes of operation are possible. On the one hand the tool-carrying frame 10 can be rigidly coupled to the upper link 8 (and also to the lower links 6). For this purpose the pin 22 is guided through a pair of drilled holes 18 and the upper link 8, as described above, is hung on the pin 22. This mode of operation is designated in the following as “rigid coupling to the upper link 8”. On the other hand a mode of operation is possible, wherein limited relative movement between the tool-carrying frame 10 and the upper link 8 is permitted. For this purpose the pin 22 is guided through the pair of elongated holes 20 and the upper link 8, as described above, is hung on the pin 22. This mode of operation is designated in the following as “upper link float position”. These two modes of operation are discussed below in detail.
In the mode of operation with rigid coupling to the upper link 8, a desired height of the coupling point of the upper link 8 can be set since the drilled holes 18 are provided at different heights. Relative movement of the tool-carrying frame 10 in relation to the lower links 6 and the upper link 8 is not possible with this mode of operation. Only the lower links 6 and the upper link 8 can move to a certain degree as known from the prior art.
The mode of operation with upper link float position is advantageous for some applications. In this mode of operation the three-point hitch 2 permits limited pivot movement upwards and downwards of the tool-carrying frame 10 and thus of the rear-mounted implement. This mode of operation is desirable particularly if the rear-mounted implement is pulled by the utility vehicle over bumps in the ground and therefore the angle position between the utility vehicle and the rear-mounted implement varies relative to the upwards and downwards direction. Even if the rear-mounted implement is raised from the utility vehicle, it may happen that due to bumps the rear-mounted implement makes contact with the ground and as a result is raised still further. This can occur for example when driving off the field with raised plough.
In order in such cases to avoid damaging or upsetting the rear-mounted implement or the three-point hitch 2, a pivot movement of the tool-carrying frame 10 about the suspension on the lower links 6 and in particular about the pivot axis s illustrated in FIGS. 1 and 2 is permitted in the mode of operation with upper link float position. In the case of the prior art tool-carrying frames 10 the long holes 22 are provided for this purpose. As a result of the movement of the pin 22 in the elongated holes 20 limited pivot movement of the tool-carrying frame 10 about the pivot axis s is permitted.
The problem with the prior art coupling of the upper link 8 to the elongated holes 20 is that this can only be done at one height. A desired height of the upper coupling point of the upper link 8 can only be set using the drilled holes 18 and therefore in the mode of operation with rigid coupling to the upper link. Furthermore up until now change-over between the mode of operation with rigid coupling to the upper link and the mode of operation with upper link float position has been comparatively time-consuming and must be done by hand. The connection between upper link 8 and tool-carrying frame 10 must be disengaged for the change-over, which means that the implement attached to the tool-carrying frame 10 must be demounted. After the change-over, settings, such as for example the distance of the implement from the ground and its inclination, must be re-adjusted accordingly. Furthermore the driver, for manual change-over, must leave the driver's seat of the utility vehicle and place the pin 22 in the desired drilled holes 18 or in the two elongated holes 20.
On the basis of FIGS. 1 and 2 a conventional back-end three-point hitch for attaching a back-end implement has been described by way of example. In this specialist area of engineering it is well-known that a front-end conventional three-point hitch for attaching a front-end implement is designed in the corresponding way.
An upper link, whose length can be adjusted manually, is described in German Patent DE 41 35 809 C1 for example. An agricultural implement, which can be attached to the front three-point hitch of a tractor, wherein an elongated hole is provided in order to permit limited pivoting of the implement, is described in German Patent DE 30 22 887 A1.
Consequently the object of the present invention consists in providing an upper link float position so that change-over between a mode of operation with upper link float position and a mode of operation with rigid coupling to the upper link can be done under load and the implement does not have to be demounted for this.
The object is achieved by an upper link according to Claim 1. Further embodiments of the invention are indicated in the sub-claims.